JP2011170468A - Load control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load control apparatus which can suppress a noise terminal voltage level while preventing the apparatus from being increased in size. <P>SOLUTION: The load control apparatus 1A includes: a main switching unit 11 which is serially connected between an AC power supply 2 and a load 3 and controls power supply to the load 3; a rectifier 12; a control part 13; an auxiliary switching unit 17 which controls the power supply to the load 3 when the main switching unit 11 is turned off; and so on. The main switching unit 11 includes a main switching element 11a of a bidirectionally controllable transistor structure. The control part 13 includes a photocoupler 13f which outputs a control signal to a control electrode of the main switching unit 11 and a low-pass filter 13b which controls an input signal to the photocoupler 13f. Since the low-pass filter 13b prolongs a rising time of the input signal to the photocoupler 13f, a load current increases smoothly and switching noise is reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a two-wire load control device connected in series between a load such as an AC power source and a lighting device.

  Conventionally, load control devices for lighting devices using contactless switching elements such as triacs and thyristors have been put into practical use. These load control devices generally have a two-wire connection from the viewpoint of reduced wiring, and are connected in series between an AC power source and a load. Thus, in the load control device connected in series between the AC power supply and the load, how to secure its own circuit power supply becomes a problem.

  The load control device 50 of the first conventional example shown in FIG. 8 is connected in series between the AC power supply 2 and the load 3, and is stable to the main switching unit 51, the rectification unit 52, the control unit 53, and the control unit 53. The first power supply unit 54 for supplying power, the second power supply unit 55 for supplying power to the first power supply unit 54 when the power supply to the load 3 is stopped, and the power supply to the load 3 are performed. The third power source unit 56 supplies power to the first power source unit 54 when it is connected, and an auxiliary opening / closing unit 57 that energizes a minute current in the load current. The switch element 51a of the main opening / closing part 51 is constituted by a triac.

  In the off state of the load control device 50 in which power is not supplied to the load 3, the voltage applied from the AC power supply 2 to the load control device 50 is supplied to the second power supply unit 55 via the rectification unit 52. The second power supply unit 55 is a constant voltage circuit composed of a resistor and a Zener diode. The current flowing through the load 3 at this time is a minute current that does not cause the load 3 to malfunction, the current consumption of the control unit 53 is small, and the impedance of the second power supply unit 55 is set to be kept high.

  On the other hand, in the ON state of the load control device 50 in which power supply to the load 3 is performed, the third power supply unit 56 is turned on by the control signal from the control unit 53, and the impedance of the load control device 50 is lowered to reduce the load. 3 and the current flowing in the third power supply unit 56 also flows in the first power supply unit 54, and charging of the buffer capacitor 54a is started. When the charging voltage of the buffer capacitor 54a becomes higher than a predetermined threshold value, the Zener diode 56a constituting the third power supply unit 56 breaks down and current starts to flow, and current flows into the gate of the auxiliary switching unit 57, The auxiliary opening / closing part 57 conducts (closed state). As a result, the current flowing from the rectifying unit 52 to the third power supply unit 56 is commutated to the auxiliary opening / closing unit 57 and further flows into the gate of the switch element 51a of the main opening / closing unit 51, and the main opening / closing unit 51 becomes conductive (closed). Status). Therefore, almost all electric power is supplied to the load 3. Once the main opening / closing part 51 becomes conductive (closed state), the current continues to flow. However, when the alternating current reaches the zero cross point, the switch element 51a self-extinguishes and the main opening / closing part 51 becomes non-conductive (open state). become. When the main opening / closing part 51 becomes non-conductive (open state), a current flows again from the rectifying part 52 through the third power supply part 56 to the first power supply part 54, and the operation for securing the self-circuit power supply of the load control device 50 is performed. . That is, the self-power supply of the load control device 50, the conduction of the auxiliary opening / closing part 57, and the conduction operation of the main opening / closing part 51 are repeated every half cycle of the alternating current.

  As a technique of the second conventional example different from the load control device of the first conventional example described above, Patent Document 1 discloses a first switch unit (main opening / closing unit) and an on-resistance that is higher than that of the first switch element. A load control device provided with a large second switch section is shown (see FIG. 1 of the document 1). This load control device is configured to turn on the first switch part after turning on the second switch part.

JP 2006-92859 A

  As described above, when the switch element of the main switching unit is a triac or thyristor as in the load control device of the first conventional example, the current supply to the load increases when the switch element is turned on. The change in the conduction impedance of the TRIAC during the transition from the OFF state to the ON state (turn-on) is discontinuous (triac and thyristor turn-on operation is a latch operation). In other words, the switching of the TRIAC is steep, Therefore, it is inevitable that the rate of change of load current per unit time increases. For this reason, the noise terminal voltage leaking to the outside from the external connection terminals 4 and 5 increases.

  In order to keep the noise terminal voltage level within a range defined by, for example, the IEC (International Electrotechnical Commission) standard, noise is generated between the triac 51a and the external connection terminals 4 and 5 as shown in FIG. A filter 58 was provided. The noise filter 58 also has a function of preventing malfunction due to noise propagated from the power supply 2 when the power supply to the load 3 is stopped. The noise filter 58 includes, for example, a capacitor connected between the external connection terminals 4 and 5 and a coil connected between the triac 51a of the main opening / closing part 51 and the capacitor. Accordingly, there is a problem that the load control device 50 is increased in size due to a capacitor and a coil mounted to suppress the noise terminal voltage level. Further, the large heat generation of the coil is a factor that prevents the load control device 50 from being downsized.

  On the other hand, in the load control device of the second conventional example shown in Patent Document 1, the circuit configuration becomes complicated as the number of switch elements increases, and the switch-on timing control becomes complicated. Become.

  The present invention has been made to solve the above-described problems of the conventional example, and an object of the present invention is to provide a load control device capable of suppressing a noise terminal voltage level while suppressing an increase in size of the device.

  In order to achieve the above object, the invention according to claim 1 is a load control device for controlling a current supply circuit to an externally connected load, has a transistor-structure switch element, and supplies power to the load. A main switching unit that controls the voltage, a rectifying unit that rectifies the voltage across the main switching unit, and a thyristor-type switching element, and controls the supply of power to the load when the main switching unit is non-conductive Auxiliary opening and closing unit, a control unit for controlling the opening and closing of the main opening and closing unit and the auxiliary opening and closing unit, power is supplied from both ends of the main opening and closing unit via the rectifying unit, and a stable voltage is supplied to the control unit And a second power supply for supplying power to the first power supply unit when power is supplied to the load from both ends of the main opening / closing unit via the rectification unit. And the main opening / closing part or the auxiliary opening In a load control device including a third power supply unit that supplies power to the first power supply unit when the unit is in a closed state and supplying power to the load, both of the switch elements of the main switching unit are The control unit includes a photo-isolating element that outputs a control signal to the control electrode of the main switching unit, and a low-pass filter that controls a signal input to the photo-isolating element. Then, the control signal output to the control electrode of the main opening / closing part is controlled to be turned on or off by conducting or blocking the output side of the optical insulating element according to the signal input through the low-pass filter. It is characterized by that.

  According to a second aspect of the present invention, in the load control device according to the first aspect, the transistor element has a lateral transistor structure, and a first electrode and a first electrode connected in series to the AC power source and the load, respectively. And a control electrode disposed between the first electrode and the second electrode, and a control signal is output from the optical insulating element to the control electrode.

  According to a third aspect of the present invention, in the load control device according to the second aspect, the control electrode and the optical isolation element are provided in two systems, and the same signal is input to the optical isolation elements of the two systems from a single low-pass filter. It is characterized by being.

  According to a fourth aspect of the present invention, in the load control device according to any one of the first to third aspects, the optical insulating element is formed of a transistor output type element.

  According to a fifth aspect of the present invention, in the load control device according to any one of the first to third aspects, the optical insulating element is configured by a MOSFET output type element.

According to the first aspect of the present invention, since the control electrode of the control unit and the main switching unit can be insulated by the optical isolation element, the driving energy consisting of the driving voltage and current of the control unit is used as the capacity of the transistor element constituting the main switching unit. It is possible to set it to the minimum without depending on it. By controlling the signal on the input side of the optical insulating element by the low-pass filter, it becomes possible to continuously change the conduction impedance of the transistor element of the main switching part, and the rate of change (di / dt) per hour of the load current can be obtained. Can be reduced. As a result, it is possible to reduce the noise terminal voltage caused by the current change without requiring the addition of a larger part than the necessity such as a coil immediately before the control electrode of the transistor element.

  According to the second aspect of the present invention, since the transistor element of the main opening / closing part is formed of a lateral transistor structure, it can be integrated on a single chip, and the high voltage AC power supply can be directly controlled by the control part. Can do.

  According to the third aspect of the present invention, since the same signal is input to the two systems of optical isolation elements from a single low-pass filter, the drive timings of the two systems of gates of the main switching unit are set to be the same. be able to.

  According to the invention of claim 4, since the output side of the photo-insulating element is a transistor element, reducing the input current makes it possible to increase only the turn-on time of the switching time of the photo-isolating element, while reducing the one turn-off time. It is possible to set so as to hardly change. Therefore, the rate of change per unit time of the load current when the main switching unit is turned on is reduced, contributing to the reduction of the noise terminal voltage level, while operating without delay when the main switching unit is shut off, and the next half of the AC voltage. There is no deviation from the cycle.

  According to the invention of claim 5, since the output side of the optical isolation element is a MOSFET, by reducing the input current, only the turn-on time of the switching time of the optical isolation element is delayed, and the one turn-off time is almost reduced. It can be set not to change. Therefore, the rate of change of the load current when the main switching unit is turned on is reduced, contributing to the reduction of the noise terminal voltage level, and operating without delay when the main switching unit is shut off, shifting to the next half cycle of the AC voltage There is no. Furthermore, the MOSFET and the control electrode of the main switching unit can be directly connected without using a buffer circuit, and the circuit configuration can be simplified and the number of parts can be reduced.

The circuit diagram which shows the structure of the load control apparatus which concerns on 1st Embodiment of this invention. The time chart which shows the signal waveform in each part of the apparatus. The figure which shows the relationship between the forward current which flows into the light emitting diode of the input side circuit of a photocoupler, and switching time. The circuit diagram which shows the structure of the modification of the load control apparatus which concerns on 1st Embodiment of this invention. The circuit diagram which shows the structure of another modification of the load control apparatus which concerns on 1st Embodiment of this invention. The circuit diagram which shows the structure of the load control apparatus which concerns on 2nd Embodiment of this invention. Sectional drawing which shows the structure of the bidirectional | two-way transistor element applied to the load control apparatus which concerns on 1st Embodiment and 2nd Embodiment of this invention. The circuit diagram which shows the structure of the load control apparatus of a 1st prior art example.

(First embodiment)
A load control device according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of the load control device 1A. The load control device 1A is connected in series between the AC power supply 2 and the load 3, and controls the main switching unit 11, the rectification unit 12, and the entire load control device 1A that control the supply of power to the load 3. A control unit 13 that performs power supply, a first power supply unit 14 that supplies stable power to the control unit 13, and a second power supply unit 15 that supplies power to the first power supply unit 14 when power to the load 3 is stopped. And a third power source unit 16 that supplies power to the first power source unit 14 when power is supplied to the load 3, and an auxiliary opening / closing unit 17 that energizes a minute current out of the load current. Has been. The load control device 1 </ b> A, the AC power supply 2, and the load 3 are connected via external connection terminals 4 and 5. The third power supply unit 16 is provided with a voltage detection unit 18 that detects a voltage input to the third power supply unit 16. The main opening / closing part 11 has a main switch element 11a having a transistor structure (see FIG. 7), and the auxiliary opening / closing part 17 has an auxiliary switch element 17a having a thyristor structure. The first power supply unit 14 has a buffer capacitor 14 a for charging the electric charge supplied to the control unit 13 when the power to the load 3 is stopped.

  The control unit 13 includes a main control unit 13e configured by a CPU, a first pulse output unit 13c, a second pulse output unit 13d, a low-pass filter 13b, an optical MOS relay 13a (see FIG. 6), or a photo An optical insulating element such as a coupler 13f and a buffer circuit 13g combined with the photocoupler 13f are provided. The main control unit 13e outputs a control signal to the first pulse output unit 13c and the second pulse output unit 13d. Two low-pass filters 13b, photocouplers 13f, and buffer circuits 13g are provided in correspondence with the gate electrode (control electrode) of the main switch element 11a. The optical MOS relay 13a will be described in a second embodiment to be described later.

  The first pulse output unit 13c receives the control signal output from the main control unit 13e and outputs the first pulse signal to the two LPFs 13b. The second pulse output unit 13d receives the control signal output from the main control unit 13e, and outputs the second pulse signal to the auxiliary switch element 17a. The low-pass filter 13b includes a resistor R, a capacitor C, and the like, and controls a signal input to the photocoupler 13f by passing only the low-frequency of the first pulse signal output from the first pulse output unit 13c. To do. A low-pass filter 13b is connected to the input side circuit of the photocoupler 13f, and a buffer circuit 13g is connected to the output side circuit. The input side circuit and the output side circuit are electrically insulated, and the main switch element is received by the phototransistor provided in the output side circuit receiving the light emitted from the light emitting diode provided in the input side circuit. The control signal 11a is output to the buffer circuit 13g. The control signal output from the photocoupler 13f is buffered via the buffer circuit 13g and input to the gate electrode of the main switch element 11a.

  FIG. 2 is a time chart showing signal waveforms in each part of the load control device 1A. The control unit 13 sets a main switching unit conduction time during which the main switching unit 11 is conducted in a half cycle of the AC power supply, and intermittently controls the current flowing through the load 3. The main control unit 13e receives the charge completion signal for the buffer capacitor 14a output from the voltage detection unit 18, and controls the first pulse output unit 13c. The first pulse output unit 13c outputs a first pulse so that the main opening / closing unit 11 is turned on only for a first predetermined time after receiving a signal from the main control unit 13e that the charging of the buffer capacitor 14a is completed. The voltage detection unit 18 may be configured to directly output a charge completion signal to the first pulse output unit 13c. That is, the first pulse rises in response to a charge completion signal from the voltage detector 18 and falls after the first predetermined time has elapsed. The signal emitted from the first pulse output unit 13c is input to the input side circuit of the photocoupler 13f via the low pass filter 13b. The signal output from the output side circuit of the photocoupler 13f is input to the gate electrode of the main switch element 11a via the buffer circuit 13g.

  The second pulse output unit 13d detects that the main opening / closing unit 11 has become non-conducting (open state), and then the second pulse output unit 13d performs the second pulse for a predetermined time so as to make the auxiliary opening / closing unit 17 conductive for a second predetermined time. Output a signal. That is, the second pulse rises when the main opening / closing part 11 becomes non-conductive (open state) and falls after the second predetermined time has elapsed.

  Since current flows from the power source 2 to the second power source unit 15 via the rectifier unit 12 even when the load control device 1A in which no power is supplied to the load 3 is in the off state, that is, when the main switching unit 11 is non-conductive. Although a minute current flows through the load 3, the current is kept low enough not to cause the load 3 to malfunction, and the impedance of the second power supply unit 15 is maintained at a high value.

  When power is being supplied to the load 3, the impedance of the third power supply unit 16 is lowered, a current is passed to the circuit side inside the load control device 1A, and the buffer capacitor 14a is charged. As described above, the third power supply unit 16 is provided with the voltage detection unit (charge monitoring unit) 18 and detects the voltage input to the third power supply unit 16, that is, the charging voltage of the buffer capacitor 14a. When the charging of the buffer capacitor 14 a is completed, the third power supply unit 16 is temporarily turned off, and the impedance of the third power supply unit 16 is lowered again in synchronization with the operation of the main opening / closing unit 11 and turned on.

  The voltage detection unit 18 is configured by, for example, a Zener diode and a transistor. When the voltage input to the third power supply unit 16 exceeds the Zener voltage of the Zener diode, the transistor is turned on and a detection signal to that effect is input to the control unit 13. During the normal operation, when receiving the detection signal from the voltage detection unit 18, the control unit 13 causes the main opening / closing unit 11 to be turned on (closed) for a first predetermined time. In FIG. 1, the first pulse output unit 13 c configured in hardware using a dedicated IC or the like so as to directly output the first pulse signal in accordance with the detection signal from the voltage detection unit 18. The example of a structure provided as a part of control part 13 is shown. Alternatively, the configuration is not limited to the illustrated configuration, and the output from the voltage detection unit 18 may be input to the main control unit 13e configured by a CPU or the like, and the first pulse signal may be output in software. . The first predetermined time for conducting the main opening / closing part 11 is preferably set to a time slightly shorter than a half cycle of the commercial frequency power supply.

  Next, when the main opening / closing part 11 starts an operation of becoming non-conductive (open state) after the first predetermined time has elapsed, the control unit 13 opens the auxiliary opening / closing part 17 for the second predetermined time (for example, several hundred μm). For 2 seconds). For this operation, the auxiliary opening / closing part 17 may be made non-conductive (open state) with a slight delay from the main opening / closing part 11. Alternatively, the main control unit 13e may output a pulse signal to the auxiliary opening / closing unit 17 that is longer than the first pulse signal output to the main opening / closing unit 11 by a second predetermined time. Alternatively, the delay circuit may be configured using a diode or a capacitor.

  With these operations, after charging of the buffer capacitor 14a is completed, power is supplied to the load 3 from the main switching unit 11 for most of the half period of the commercial AC power supply, and then the energization current decreases. Then, electric power is supplied from the auxiliary opening / closing unit 17 to the load 3. At this time, since the first predetermined time is set so that the main opening / closing part 11 is turned off before the time when the current value becomes zero (zero crossing point), the main opening / closing part 11 exceeds the zero crossing point. There is no conduction. Since the auxiliary opening / closing section 17 includes the auxiliary switch element 17a having a thyristor structure, the auxiliary opening / closing section 17 becomes non-conductive (open state) when the current value becomes zero (zero cross point). When the auxiliary opening / closing part 17 becomes non-conductive (open state), the current again flows into the third power supply part 16, and thus the above operation is repeated every 1/2 cycle of the commercial power supply.

  In the present embodiment, the rise time of the first pulse signal input to the photocoupler 13f can be increased by the low-pass filter 13b interposed between the first pulse output unit 13c and the photocoupler 13f. As the rise time of the first pulse signal becomes longer in the low-pass filter 13b, the transient response time of the output signal of the photocoupler also becomes longer. Thereby, the turn-on time of the main switch element 11a of the main switching unit 11 can also be set late, and the amount of change per unit time of the load current related to the turn-on time of the main switching unit 11 can also be reduced. Here, the load current is a current that flows into the load control device 1A from the external connection terminal 4 and flows out of the external connection terminal 5 and flows into the load 3. Since the power source 2 is an AC power source, the load current flows from the external connection terminal 5 into the load control device 1A and changes from the external connection terminal 4 when the polarity changes after the time corresponding to half of the period determined by the frequency has elapsed. It will be leaked.

  In general, when the main switching unit 11 is turned on, a discontinuity point in the rate of change of load current per unit time occurs, and this causes power lines (that is, AC power supply 2, load 3, external connection terminals 4, 5). , And a circuit constituted by the main switching unit 11). In the present embodiment, since the main switch element 11a of the main switching unit 11 has a transistor structure, the conduction impedance can be continuously changed, and the rate of change of load current per unit time (di / dt) can be reduced, and the switching noise described above can be suppressed.

  FIG. 3 shows the relationship between the forward current flowing in the light emitting diode of the input side circuit of the photocoupler 13f and the switching time. As shown in FIG. 3, the turn-on time of the signal passing through the photocoupler 13f and the buffer circuit 13g (the time required for the control signal of the main switch element 11a of the main switching unit 11 to switch from the off state to the on state) is a forward current. The turn-on time is significantly increased when the forward current is reduced. On the other hand, the turn-off time of the signal that passes through the photocoupler 13f and the buffer circuit 13g (the time required for the control signal of the main switch element 11a of the main switching unit 11 to switch from the on state to the off state) is less dependent on the forward current. Even if the forward current decreases, the turn-off time is only slightly reduced. Therefore, the main switch element 11a of the main switching unit 11 that is controlled to be opened / closed by the switching operation of the photocoupler 13f can also set the switching time at the time of turn-on slower. Thereby, the load current rises smoothly, the switching noise generated at the time of turn-on is reduced, and the noise leaked to the outside from the external connection terminals 4 and 5 due to the switching operation of the main switching unit 11 of the load control device 1A. The terminal voltage can be suppressed. In addition, since the switching time when the main switch element 11a is turned off does not change greatly, before the next zero cross point of the load current arrives, the main switching unit 11 is opened (non-conducting state), and the auxiliary switching unit 17 is Closed state (conducting state). Thereafter, when the zero cross point of the load current is reached, since the auxiliary switch element 17a of the auxiliary switching unit 17 has a thyristor structure, the auxiliary switching unit 17 is opened (non-conducting) by the arc extinguishing action of the thyristor. Further, when the next half cycle is entered beyond the zero cross point, the operation of the current flowing into the third power supply unit 16 starts again. In this way, the repeated operation every half cycle is not impaired.

  4 and 5 show a modification of the load control device 1A. The load control device 1B shown in FIG. 4 is an example in which the input side circuits of two photocouplers 13f are connected in series. The load control device 1C shown in FIG. 5 has the input side circuits of two photocouplers 13f in parallel. This is possible with connected examples. Both the load control device 1B and the load control device 1C output the same signal from the single low-pass filter 13b to the two systems of photocouplers 13f. The configurations of the output side circuit and buffer circuit 13g of the two systems of photocouplers 13f are the same as those of the load control device 1A. According to the load control device 1B and the load control device 1C, since the same signal is input from the single low-pass filter 13b to the two systems of photocouplers 13f, the drive timings of the two systems of gates of the main switch element 11a are simultaneous. Can be set to be

(Second Embodiment)
A load control device according to a second embodiment of the present invention will be described. FIG. 6 shows the configuration of the load control device 1D. In the load control device 1D, a MOSFET output type optical MOS relay 13a is applied instead of the photocoupler 13f as an optical insulating element in the load control device 1B, and the two buffer circuits 13g are omitted accordingly. This is different from the first embodiment. The optical MOS relay 13a is an optical insulating element in which a light emitting diode is applied to an input side circuit and a MOSFET is applied to an output side circuit.

  The optical MOS relay 13a has the same tendency as the signal passing through the photocoupler 13f and the buffer circuit 13g shown in FIG. 3 in the relationship between the forward current flowing through the light emitting diode of the input side circuit and the switching time. That is, the turn-on time of the optical MOS relay 13a is highly dependent on the forward current, and when the forward current decreases, the turn-on time becomes significantly longer. On the other hand, the turn-off time of the optical MOS relay 13a has a low dependency on the forward current, and even if the forward current is reduced, the turn-off time is only slightly shortened. Accordingly, the main switch element 11a of the main switching unit 11 that is controlled to be opened and closed by the switching operation of the optical MOS relay 13a can also set the switching time at the time of turn-on slower. Thereby, it is possible to suppress the noise terminal voltage resulting from the switching operation of the main switching unit 11 of the load control device 1A. In addition, since the switching time when the main switch element 11a is turned off does not change greatly, before the next zero cross point of the load current arrives, the main switching unit 11 is opened (non-conducting state), and the auxiliary switching unit 17 is Closed state (conducting state). Thereafter, when the zero cross point of the load current is reached, since the auxiliary switch element 17a of the auxiliary switching unit 17 has a thyristor structure, the auxiliary switching unit 17 is opened (non-conducting) by the arc extinguishing action of the thyristor. Further, when the next half cycle is entered beyond the zero cross point, the operation of the current flowing into the third power supply unit 16 starts again. In this way, the repeated operation every half cycle is not impaired. Also, the optical MOS relay and the gate electrode of the main switch element 11a of the main switching unit 11 can be directly connected without going through the buffer circuit 13g shown in FIG. 3, simplifying the circuit configuration and reducing the number of parts. It becomes possible to reduce.

(Horizontal transistor element)
Hereinafter, a lateral transistor element capable of bidirectional control applied as the main switch element 11a in the first embodiment and the second embodiment will be described. FIG. 7 shows a schematic configuration of a lateral transistor element capable of bidirectional control. Such a lateral transistor element is called an HFET (Heterostructure Field-Effect Transistor), and uses a two-dimensional electron gas layer generated at the AlGaN / GaN hetero interface as a channel layer. 3, a first electrode 6 and a second electrode 7 connected in series to each other. Further, the first gate electrode 21 and the second gate electrode 22 are formed so that a high withstand voltage can be maintained with respect to the first electrode 6 and the second electrode 7 when energization is turned off.

  The main switch element 11a having a bidirectional transistor structure has a buffer layer 24 formed by alternately laminating aluminum nitride (AlN) and gallium nitride (GaN) on a substrate 23 made of silicon (Si), on which a buffer layer 24 is formed. A semiconductor layer stack 25 is formed. In the semiconductor layer stack 25, a first semiconductor layer and a second semiconductor layer having a band gap larger than that of the first semiconductor layer are sequentially stacked from the substrate side. The first semiconductor layer is an undoped gallium nitride (GaN) layer 26, and the second semiconductor layer is an aluminum gallium nitride (AlGaN) layer 27. In the vicinity of the heterointerface between the GaN layer and the AlGaN layer, charges are generated due to spontaneous polarization and piezoelectric polarization. Thereby, a channel region which is a two-dimensional electron gas (2DEG) layer having a high electron mobility is formed.

  A first ohmic electrode 28 and a second ohmic electrode 29 are formed on the semiconductor layer stack 25 at a distance from each other. The first ohmic electrode 28 and the second ohmic electrode 29 form an ohmic junction with the channel region. In FIG. 7, in order to reduce the contact resistance, a part of the AlGaN layer is removed and the GaN layer is dug so that the first ohmic electrode 28 and the second ohmic electrode 29 are connected to the interface between the AlGaN layer 27 and the GaN layer 26. The form formed so that it may contact | connect is shown. Note that the first ohmic electrode 28 and the second ohmic electrode 29 may be formed on the AlGaN layer 27.

  In the region between the first ohmic electrode 28 and the second ohmic electrode 29 on the AlGaN layer 27, the first p-type semiconductor layer 30 and the second p-type semiconductor layer 31 are spaced apart from each other. Is formed. A first gate electrode 21 is formed on the first p-type semiconductor layer 30, and a second gate electrode 22 is formed on the second p-type semiconductor layer 31. The first gate electrode 21 and the second gate electrode 22 are each formed by stacking palladium (Pd) and gold (Au), and the first p-type semiconductor layer 30 and the second p-type semiconductor layer 31 are ohmic. In contact. Further, a protective film 32 made of silicon nitride (SiN) is formed so as to cover the AlGaN layer 27, the p-type semiconductor layer 30 and the second p-type semiconductor layer 31. By forming the protective film 32, it is possible to compensate for a defect that causes so-called current collapse and to improve current collapse. The first p-type semiconductor layer 30 and the second p-type semiconductor layer 31 and the AlGaN layer 27 form PN junctions. As a result, when the voltage between the first ohmic electrode 28 and the first gate electrode 21 is 0 V, for example, the depletion layer spreads from the first p-type GaN layer 30 into the channel region. Can be blocked. Similarly, when the voltage between the second ohmic electrode 29 and the second gate electrode 22 is, for example, 0 V or less, a depletion layer spreads from the second p-type GaN layer 31 into the channel region, and therefore flows into the channel. A semiconductor capable of interrupting current and performing a so-called normally-off operation is realized.

  Hereinafter, the potential of the first ohmic electrode 28 is V1, the potential of the first gate electrode 21 is V2, the potential of the second gate electrode 22 is V3, and the potential of the second ohmic electrode 29 is V4. In this case, if V2 is higher than V1 by 1.5V or more, the depletion layer extending from the first p-type semiconductor layer 30 into the channel region is reduced, so that a current can flow through the channel region. Similarly, if V3 is higher than V4 by 1.5V or more, the depletion layer extending from the second p-type semiconductor layer 31 into the channel region is reduced, and a current can flow through the channel region. The threshold voltage of the first gate electrode 21 at which the depletion layer extending in the channel region below the first gate electrode 21 is reduced and current can flow through the channel region is set to the first threshold value. The threshold voltage of the second gate electrode 22 at which the depletion layer extending into the channel region on the lower side of the second gate electrode 22 is reduced and the current can flow through the channel region is set to the value voltage. The threshold voltage is 2. That is, the first threshold voltage and the second threshold voltage are both 1.5V. The distance between the first p-type semiconductor layer 30 and the second p-type semiconductor layer 31 is set so as to withstand the maximum voltage applied to the first ohmic electrode 28 and the second ohmic electrode 29. Has been. A gate drive signal (that is, a control signal to the first gate terminal) is input between the first ohmic electrode 28 and the first gate electrode 21. Similarly, a gate drive signal (that is, a control signal to the second gate terminal) is input between the second ohmic electrode 29 and the second gate electrode 22. The first electrode 6 is connected to the first ohmic electrode 28, the second electrode 7 is connected to the second ohmic electrode 29, the first gate terminal 33 is connected to the first gate electrode 21, and the second The gate terminal 34 is connected to the second gate electrode 22. (Reference T. Morita, et.al, IEEE International Electron Devices Meeting, pp. 865-868, December 2007)

  When the main switching unit 11 is non-conductive, a low level signal is applied to the gate electrode from the control unit 13, but the potential is higher than the lowest potential of the main switching unit 11 by one diode of the rectification unit 12. . Here, if the threshold value for switching between conduction (closed state) / non-conduction (open state) of the main opening / closing part 11 is sufficiently higher than the potential of one diode, the non-conduction (open state) is surely maintained. can do. On the other hand, when the main opening / closing part 11 is in the conductive state (closed state), the above-described operation is performed. Therefore, the high voltage AC power supply can be directly controlled by the control unit driven by the control signal of several volts. Further, by using an HFET having a high electron mobility in this way, it is possible to realize a small and high capacity 2-wire load control device.

  The present invention is not limited to the configuration of the above-described embodiment, and at least the main switch element 11a of the main switching unit 11 is configured by a transistor element capable of bidirectional control, and a control signal is applied to the gate electrode of the main switching unit 11. An optical insulating element such as the photocoupler 13f or the optical MOS relay 13a to output and a low-pass filter 13b for controlling a signal input to the optical insulating element may be provided. The present invention can be modified in various ways. For example, the main switch element 11a constituting the main opening / closing portion 11 may be a switch element that can be controlled in both directions, and is configured by a plurality of single-gate transistor elements. It may be what has been done. In the case of a plurality of single-gate transistor elements, it may be a vertical transistor element or a horizontal transistor element. The auxiliary switch element 17a constituting the auxiliary opening / closing part 17 may be a triac.

  In addition, the low-pass filter 13b is preferably inserted between the first pulse output unit 13c and the photocoupler 13f or the optical MOS relay 13a in consideration of the capacitance of the capacitor as its component, but the photocoupler 13f Alternatively, it may be interposed between the optical MOS relay 13 a and the main opening / closing part 11. That is, the low-pass filter 13b may be provided in a path from the first pulse output unit 13c to the main opening / closing unit 11 so as to lengthen the rising time of the first pulse signal.

DESCRIPTION OF SYMBOLS 1A Load control apparatus 2 AC power supply 3 Load 11 Main switching part 11a Main switch element 12 Rectification part 13 Control part 13a Optical MOS relay (optical insulation element)
13b Low-pass filter 13c 1st pulse output part 13d 2nd pulse output part 13e Main control part 13f Photocoupler (optical insulation element)
13g Buffer circuit 14 1st power supply part 15 2nd power supply part 16 3rd power supply part 17 Auxiliary opening / closing part 17a Auxiliary switch element

Claims (5)

A load control device that controls a current supply circuit to a load connected to the outside,
A main switching unit having a transistor-structure switch element and controlling supply of power to a load;
A rectifying unit for rectifying the voltage across the main switching unit;
An auxiliary opening / closing part having a switch element of a thyristor structure and controlling the supply of power to a load when the main opening / closing part is non-conductive;
A control unit that controls opening and closing of the main opening and closing unit and the auxiliary opening and closing unit;
A first power supply unit that is supplied with power from both ends of the main switching unit via the rectification unit and supplies a stable voltage to the control unit;
A second power supply unit that supplies power to the first power supply unit when power is supplied from both ends of the main switching unit via the rectification unit and power supply to the load is stopped;
In the load control device including a third power supply unit that supplies power to the first power supply unit when the main opening / closing unit or the auxiliary opening / closing unit is in a closed state and supplying power to the load,
The switch element of the main opening / closing part is composed of a bidirectionally controllable transistor element,
The control unit includes an optical insulating element that outputs a control signal to a control electrode of the main opening and closing unit, and a low-pass filter that controls a signal input to the optical insulating element,
The control signal output to the control electrode of the main opening / closing part is controlled to be turned on or off by conducting or blocking the output side of the optical insulating element according to the signal input through the low-pass filter. A characteristic load control device. The transistor element has a lateral transistor structure, and is disposed between a first electrode and a second electrode connected in series to the AC power supply and a load, and the first electrode and the second electrode, respectively. Having a control electrode,
The load control device according to claim 1, wherein a control signal is output from the optical isolation element to the control electrode. The control electrode and the optical insulating element are provided in two systems,
The load control device according to claim 2, wherein the same signal is input to the two systems of optical isolation elements from a single low-pass filter.   The load control device according to any one of claims 1 to 3, wherein the optical insulating element is configured by a transistor output type element.   The load control device according to any one of claims 1 to 3, wherein the optical isolation element is configured by a MOSFET output type element.

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